WEDNESDAY, Dec. 28 (HealthDay News) -- A new examination of the origin of syphilis supports the theory that the sexually transmitted disease was carried to Europe aboard Christopher Columbus' ships as they sailed home from the New World.

The disease was not spread through sexual contact at the time, but adapted to survive once it got to Europe, Emory University researchers say.

"Syphilis has been around for 500 years," study co-leader Molly Zuckerman, a former Emory graduate student who is now an assistant professor at Mississippi State University, said in an Emory news release. "People started debating where it came from shortly afterwards, and they haven't stopped since. It was one of the first global diseases, and understanding where it came from and how it spread may help us combat diseases today."

After analyzing skeletal evidence in 54 published reports, the researchers found that syphilis did not exist in Europe until after Columbus' historic voyage to the New World in 1492. They said that most of the skeletal material lacked characteristics that would meet standard diagnostic criteria for chronic syphilis, such as small holes on the skull and long bones.

It appears that skeletons previously considered evidence of syphilis in Europe before Columbus' trip were dated incorrectly because of seafood consumption, which would have altered the collagen levels of the skeletons, the researchers said.

Their appraisal is published in the Yearbook of Physical Anthropology.

"This is the first time that all 54 of these cases have been evaluated systematically," said study co-author George Armelagos, an anthropologist at Emory, in the news release. "The evidence keeps accumulating that a progenitor of syphilis came from the New World with Columbus' crew and rapidly evolved into the venereal disease that remains with us today."

The researchers suggested someone sailing with Columbus brought Treponema -- the bacteria that causes syphilis -- to Europe. This type of bacteria also causes other diseases that are spread through skin-to-skin or oral contact in tropical climates. Their theory is that the bacteria mutated into the sexually transmitted form to survive in the cooler and more sanitary conditions of Europe.

"In reality, it appears that venereal syphilis was the byproduct of two different populations meeting and exchanging a pathogen," Zuckerman said. "It was an adaptive event, the natural selection of a disease, independent of morality or blame."

The researchers said more study is needed to confirm their findings. "The origin of syphilis is a fascinating, compelling question," Zuckerman said. "The current evidence is pretty definitive, but we shouldn't close the book and say we're done with the subject. The great thing about science is constantly being able to understand things in a new light."